Optical appliance.



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E. c. BRIDGE. UPTIGAL APPLIANCE. (Application med .rune 1o, 189s.)

(No Model.)

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EPHRAIM O. BRIDGE, OF OHARITON, IOWA.

OPTICAL APPLIANCE.

SPECIFICATION forming part of Letters Patent No. 638,316, dated December5, 1899.

Application iiled .Tune 10, 1898. Serial No. 683,079. (No model.)

To a/ZZ whom t may concern:

Be it known that I, EPHRAIM C. BRIDGE, a citizen of the United States,residing at Chariton, in the county of Lucas and State of Iowa, haveinvented certain new and useful Improvements in Optical Appliances; andI do declare the following to be a full, clear, and exact description ofthe invention, such as will enable others skilled in the art to which itappertains to make and use the same, reference being had to theaccompanying drawings, and to the lett-ers of reference marked thereon,which form a part of this specification.

This invention is directed to improvements indevices for measuringoptical defects or irregularities of the eye commonly known as errors ofrefraction,and also for determining the character and strength ot'remedial lenses and for applying tests thereto while in use. I

Myinvention contemplates the employment, in connectionwith an adjustablenegative lens, of a plurality of converging lenses, whereby sphericalaberration is corrected and the maximum of illumination obtained, andwhereby also the light-rays are so disposed as to completely cover thecornea of the eye, thus rendering the device particularly adaptable forcorrecting presbyopia in addition to measuringother defects of sight.

I'Ieretofore, so far as I am aware, in devices of this character nomeans have been devised which successfully overcome spherical aberrationof the lens except at the expense of illumination. It has been proposedto employ a single lens in conjunction with a fixed negative lens, butwith such an arrangement not only is spherical aberration present, butby reason of'this defect a clear vision is not possible. My improvedoptical device is designed to accurately detect and record the extent ofvision, the presbyopia, and astig-V matism, and if the latter is presentfurther adjustment will determine the kind and amount of astigmatism. Itis also possible with my improved applianceto test glasses while in useby the patient and determine what changes, if any, are to be madetherein. Moreover, it is possible with my device to detect and measurehypermetropia when presbyopia is absent.

The nature of my invention will be readily understood by reference tothe following detailed description and to the accompanying drawings, inwhich- Figure l is a view in elevation of an optical appliance embodyingmy invention. Fig. 2 is a central sectional view. Figs. 3 and 4 aredetail views of alternate forms of` lenses for use in connection with myimproved device.

Referring to the said drawings by letter, A denotes the main tube, B isa tube extension of the main tube, O is the draw-tube, and D is astandard on which the tubes are supported, a pivotal connect-ion beingmade at ai. The draw-tube O is slidably arranged in the tube extensionB, and to permit of its manipulation a pin o is provided on the tube Cand projects through a slot in the extension. In one end of thedraw-tube is a concave or negative lens e. In the upper side oit' thetube extension are slots b b for test-lenses, and b is a sleeve forcovering the slots when not in use. In the opposite end of the main tubeis slidably. arranged an innertube F, which carries a combination oflenses, hereinafter referred to. This tube F is longitudinally ad=justed through the employment ofa pinion u, rotated by a hand-wheelt,the pinion engaging a rack-bar s, carried by the inner tube F. At theouter end of the tube F is a hoodf.

I employ in connection with the inner tube F a plurality of converginglenses, Fig. 2, showing a combination of convexo-convex andconcave-concave lenses,and Figs. 3 and 4 showing, respectively,combinations of conveXo-convex and concavoconvex lenses, and ofconvexe-convex,concavo-concave,and concavo-conveX lenses. Each of thecombinations shown minimizes spherical aberration and produces themaximum illumination,and, in conjunction with the negative lens, sodisposes the light-rays as that the cornea of the applied eye iscovered, the result being an absolute clear vision.

In connection with the inner slide-tube F, I employ a scale (see Fig. l)by which the char acter of lens is determined. The measurementwhen mademay be proven by a test of the glasses when Worn, whereby absolute accuracy is obtained. In` measuring presbye opia, for instance, the eye ofthe patient is applied4 to the device and the tube F is adL IOC justeduntil the image is perfectly visible, and by reference to the scale thecharacter of glass is at once determined, and this Without regard to theage of the patient.

The negative lens is, as before stated, mounted in a draw-tube, which ismanipulated from without by the pin u. An adjustment of this lens isnecessary When a variation in the distance between the device and testobject is made, the object being to insure accuracy of scale indicationsregardless of change of distance.

I claim as my invention- In an optical instrument of the characterdescribed, the combination of a main tube provided toward one end with arelatively small slidable tube carrying a negative lens, and providedtoward its other end with a relatively large slidable tube telescopingthe main tube, means for effecting the adjustments of these slide-tubes,a plurality of converging lenses in the larger slide-tube, and anindieating-scale in connection with the latter tube and main tube. i

In testimonywhereof I afx my signature in presence of two Witnesses.

EPHRAIM C. BRIDGE. Witnesses:

JOHN CULBERTSON, PETER E. VAIL.

